A thermoplastic resin has excellent chemical resistance, mechanical strength, and electrical insulation, to be widely used in a housing, a connector, and the like, of electrical, electronic, and automobile components. In the case in which the thermoplastic resin is used for electrical and electronic device fields, it is necessary to impart flame-retardancy in order to secure safety against a fire.
A flame-retardant has an influence on the safety of the thermoplastic plastic during a preparing process in a molten state thereof. A large amount of the flame-retardant should be used in order to satisfy an appropriate flame-retardancy of a plastic according to international standards. In addition, a chemical reaction is required at a high temperature to implement flame-retardancy, such that the flame-retardant may damage a processing stability of the plastic. For example, polymer degradation, a cross linking reaction, gas release or decoloration may be increased. In addition, in the above-described process, a halogen-based gas is generated by pyrolysis, thereby causing deterioration in working environment due to corrosion of devices such as a molding device, a die, and the like, and a toxic gas.
In particular, it is found that the case of using a phosphoric flame-retardant in polyethylene and polypropylene is not sufficient for reducing problems caused by the processes such as the decoloration and the degradation of the resin.
The following patent documents such as PCT/EP97/01664 and Germany Laid-Open Publication Nos. 19734437 and 19737727 disclose that a flame-retardancy may be increased by blending a main flame-retardant with other flame-retardants as a flame-retardant synergistic as compared to the case of using the main flame-retardant alone. In addition, they disclose that an example of the synergistic may include melamine and a melamine compound (melamine cyanurate and melamine phosphate), which may independently impart some degree of flame-retardancy to any kind of thermoplastic plastic, however, significantly improved effects obtained by blending with a phosphinic acid, or the like.
Recently, a piperazine pyrophosphate compound has become interested in that it has remarkable effects as one component of a flame-retardant composition added in a synthetic resin. A method for preparing the piperazine pyrophosphate has been largely reported. For example, Japanese Patent Laid-Open Publication No. Sho 47-88791 discloses a piperazine pyrophosphate as a sparingly water-soluble precipitate, which is obtained by reacting a piperazine hydrochloride salt with sodium pyrophosphate in an aqueous solution. In addition, U.S. Pat. Nos. 3,810,850 and 4,599,375 disclose that a method of preparing a piperazine pyrophosphate as a precipitate obtained by reacting piperazine (anhydride) with sodium pyrophosphate (anhydride) in an aqueous solution, followed by treatment with a hydrochloric acid. However, research into a piperazinic acid metal salt compound has not been found. In particular, it may be appreciated that piperazine diphosphate present as an intermediate is water-soluble and has an excellent flame-retardancy, but has a difficulty in treatment, such that piperazine diphosphate is prepared as a metal salt compound to thereby be utilized as a flame-retardant having a structural safety and excellent quality.
In addition, it is well known that sodium chloride, or the like, is produced as an impurity generated by the above-described preparation, resulting in negative effects at the time of being applied to a semiconductor, an electronic device, or the like. Further, according to the above-described preparation, the thus-prepared product has a low yield, a raw material is expensive, and cost for treating waste is required. In addition, since piperazine diphosphate having good flame-retardancy is water-soluble, which is one of the biggest problems, it has difficulty in being applied to a resin and treatment.
In the case in which piperazine diphosphate or piperazine pyrophosphate is used as one component of the flame-retardant composition, at least about 30 wt % or more as an amount thereof, which is a large amount, should be treated in order to show V—O flame rating retardancy except for the effect of the impurity. Therefore, the large amount of expensive piperazine pyrophosphate is not significantly effective in view of an economical aspect.